Queue examples

These examples enqueue two reports and dequeue them in arrival order.

Python

from collections import deque

def print_label_value(label, value):
    print(f"\033[1;36m{label}:\033[0m {value}")

def queue_state(queue):
    return ", ".join(queue) if queue else "empty"

waiting_reports = deque()
waiting_reports.append("GS-2042")
print_label_value("1. Enqueue GS-2042", queue_state(waiting_reports))

waiting_reports.append("GS-2043")
print_label_value("2. Enqueue GS-2043", queue_state(waiting_reports))

print_label_value("3. Dequeue", waiting_reports.popleft())
print_label_value("4. Dequeue", waiting_reports.popleft())
print_label_value("5. Queue status", queue_state(waiting_reports))

JavaScript

function printLabelValue(label, value) {
  console.log(`\x1b[1;36m${label}:\x1b[0m`, value);
}

class Queue {
  constructor() {
    this.items = [];
    this.front = 0;
  }

  enqueue(value) {
    this.items.push(value);
  }

  dequeue() {
    if (this.isEmpty()) {
      throw new Error("cannot dequeue from an empty queue");
    }
    const value = this.items[this.front];
    this.front += 1;
    return value;
  }

  isEmpty() {
    return this.front >= this.items.length;
  }

  state() {
    return this.isEmpty() ? "empty" : this.items.slice(this.front).join(", ");
  }
}

const waitingReports = new Queue();
waitingReports.enqueue("GS-2042");
printLabelValue("1. Enqueue GS-2042", waitingReports.state());

waitingReports.enqueue("GS-2043");
printLabelValue("2. Enqueue GS-2043", waitingReports.state());

printLabelValue("3. Dequeue", waitingReports.dequeue());
printLabelValue("4. Dequeue", waitingReports.dequeue());
printLabelValue("5. Queue status", waitingReports.state());

Expected output

1. Enqueue GS-2042: GS-2042
2. Enqueue GS-2043: GS-2042, GS-2043
3. Dequeue: GS-2042
4. Dequeue: GS-2043
5. Queue status: empty